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[W9IQ]

Part 97 requires the signal level in the 1-1000 MHz band to be below S9 at 100 feet.

There is no such Part 97 provision.

- Glenn W9IQ

So what's a typical S-meter reading, 98.43 feet away for something throwing 30 microVolts/Meter of RF into some HF band via A/C power cord and/or USB cable (etc.) antennas?

As you are probably aware, you did not provide enough information to answer the question. Nor is the question relevant to any FCC regulation.

Despite the repeated claim, there is no such Part 97 or Part 15 requirement. One glaring point is that FCC never uses "S units" as a basis of measurement. If you believe there is such an FCC requirement, then cite the relevant sub-section. I would then be happy to discuss the specifics.

- Glenn W9IQ

[RFRY]

... Part 97 requires the signal level in the 1-1000 MHz band to be below S9 at 100 feet. . ...

Notice that the signal strength displayed by the S meter of a receiver is only a relative value, based on the conducted value of the r-f voltage applied to its input connector.  It is not an absolute measure of the field intensity arriving at the receive antenna, which is measured in units or sub-units of volts/meter.

The r-f voltage present at the input connector of a receiver on a given frequency depends on:

• the e-m wave energy radiated by the transmit system in all directions,
• the gain of the receive antenna system in the direction(s) of the arriving signal(s),
• the test frequency in kHz/MHz (etc), and
  
• the propagation environment.

It is difficult (and expensive) to accurately measure the field intensity of a radiated e-m wave.  Normally that is ~impossible without using a calibrated test range and calibrated test equipment when making the measurement.

S meter readings cannot be used to prove or dis-prove compliance to any regulatory limit(s).

[K0UA]

Agreed, if you took 10 different receivers and hooked them to the same antenna on a test range one after the other with a calibrated signal generator on the other end of the test range you would likely get 10 different readings. S meters are only So-So calibrated at even the S9 reading, and no one can agree what each S unit should be. They vary by as much as 100 percent, and are not linear to boot.

When people compare antenna A to B across thousands of miles, it has no meaning, nor two different stations as a comparison side by side. Propagation changes second by second and these type of test while fun to do, are pretty meaningless. Unless it is consistently done over a long period of time, where Station A is always stronger than Station B.  But a simple Station A to Station B test done over a period of seconds means nothing.

[N5PNZ]

I found my biggest noise problem was a "security" (street) light at the back edge of my property.  It was owned by the power company but I was paying for it.  The photo cell on it was defective so it never turned off.  I had the power company turn it off and my vertical noise level dropped by 4 S units. 
But since then a S7 buzz has appeared on both vert and horizontal.  The noise blanker will nullify it but then I have strong signal distortion.  The noise may have to do with a new neighbor that moved in next door about the same time.  On a hand held HF receiver it is strongest in that direction.    When she gets off her Covid quarantine I may ask her if she has one of those stinking "touch" lamps.  It could be a charging station too though.  If it is I don't know what I can do about it at this point.

[N0BAF]

Someone needs to invent a bug tracker that can be used to locate sources RF energy that might be bugs and a series of bug blockers that consumers can install to block the RF energy emitted by a presumed bug.

[W3PX]

Someone needs to invent a bug tracker that can be used to locate sources RF energy that might be bugs and a series of bug blockers that consumers can install to block the RF energy emitted by a presumed bug.

If you are referring to "bugs" in the sense of eavesdropping devices, there is an entire field called TSCM (Technical Surveillance Counter-Measures) devoted to that subject. Devices and techniques to mitigate bugs have existed for decades.

Locating RF-based bugs can be as simple as sweeping an area with a spectrum analyzer and a small hand held directional antenna.

"Blocking" the RF energy emitted by a bug is not very productive as it requires a relatively high jamming power that raises the local noise floor. A better approach is to locate the bug, then place it in a faraday shield until it can be analyzed. Paint cans, aluminum foil, and fine wire mesh can be used to wrap small bugs to prevent RF radiation until the device can be analyzed in a screen room or destroyed.

73 Frank W3PX

[N0BAF]

Locating RF-based “bugs” can be as simple as sweeping an area with a spectrum analyzer an AM radio and a small hand held directional antenna.

Fixed that for you.

The average person isn’t going to hire a professional to sweep their house. But if it was something they could do themselves using tools they already have they might just do it. And when they find that CFL transmitting who knows what they might decide to replace it or snap a ferrite on the cord just in case.